Repeated concussion among U.S. military personnel during Operation Iraqi Freedom.

Concussions are a predominant injury of the conflicts in Iraq and Afghanistan. The aims of this study were to describe repeated concussive events among U.S. military personnel injured in Operation Iraqi Freedom and examine subsequent healthcare utilization. We reviewed clinical records from the Expeditionary Medical Encounter Database to identify service members with repeat concussions. We abstracted demographic and injury-specific variables, calculated time between events, and identified healthcare utilization from electronic medical databases. Overall, 113 personnel experienced more than one concussion between 2004 and 2008. A majority of these incidents were blast related. The median time between events was 40 days, with 20% experiencing a second event within 2 weeks of the first and 87% within 3 months. Time between events was not associated with severity of the second event. Greater severity of the second concussive event was associated with higher postinjury utilization of mental health and neurology services. This study is one of the first to describe repeated concussions in a combat setting. We found that repeated concussions occur within a short interval among deployed personnel, although the effects of the first event are unclear. Further research is needed to define the effect of repeated concussions on the health of combat veterans.